1. Field of the Invention
The present invention pertains to multi-touch input systems and methods, and more particularly to a mixture of chord keying, gesture recognition and touch typing techniques.
2. The Related Art
The primary use of chords, or simultaneous finger presses, within the data entry art has been in chord keying schemes that map each letter of the alphabet or even shorthand word parts to a different finger combination. This allows chord keyboards to have a reduced number of keys, often limited to a home row of keys. This in turn reduces finger travel and potentially speeds typing. Some schemes, like U.S. Pat. No. 5,281,966 to Walsh, adopt a mapping that is sensibly organized so as to be easy to learn and remember, while others, such as U.S. Pat. No. 5,642,108 to Gopher et al., emphasize long-term keying performance by assigning the most frequently entered letters of the alphabet to those finger combinations that are quickest and easiest to perform. In U.S. Pat. No. 5,808,567, McCloud discloses a scheme for communicating with three-finger chords. In this system, a touch of the index finger on one of nine regions of a small selector pad can be modified by thumb and/or middle finger presses on switch pads adjacent to the selector pad.
The recent development of multiple-touch sensitive surfaces that lack the restrictions of distinct mechanical keys warrants a reexamination of chording schemes. Direct adaptation of the chord keying schemes cited above to a multi-touch surface certainly seems feasible, but may not be desirable. U.S. Pat. No. 5,825,352 to Bisset et al. describes a touchpad with row and column electrodes that produces pointing in response to single finger motion and dragging in response to two finger motion. U.S. Pat. No. 6,107,997, Ure utilizes the touch sensor array of U.S. Pat. No. 5,194,862 and interprets single finger motions as pointing while interpreting various placements of a 2-finger chord on a grid as key entry. In U.S. application Ser. No. 09/236,513, however, Westerman and Elias take yet another approach, interpreting asynchronous touches on a multi-touch surface (MTS) as conventional single-finger typing while interpreting motions initiated by chords as pointing, clicking, and other gesture commands. We prefer this approach for the following reasons: learning a few new chords for graphical manipulation is much easier than learning a slew of new chords for typing the whole alphabet, and graphical manipulation seems a better use of chords in today""s graphics intensive computing environment. In dictation situations where greater text entry speeds are needed than can be achieved with non-chordic keying, adopting a continuous speech recognition system for text entry is becoming more practical than learning a chord keying technique.
Non-chordic touch typing on surfaces that provide limited tactile feedback presents its own difficulties. If the typist is not careful, the hands or individual fingers tend to drift out of alignment with the key layout, or more particularly with the home row of keys where hands normally rest. Reaching for punctuation and modifier keys located on the periphery of QWERTY computer keyboard layouts exacerbates this drift. Though the Shift modifier key is not particularly far from the home row keys, the direction of pinky motion needed to reach Shift strongly pulls the other fingertips off their alignment with home row. Since the Shift modifier key must be reached so frequently to capitalize words, even typists using mechanical keyboards have long complained about the awkward pinky twist and ulnar deviation at the wrist necessary to hold it down. Accurately hitting the Shift keys becomes, if anything, more awkward on a relatively smooth surface that does not give like a mechanical key.
In the related ergonomic and chord keyboard art exemplified by FIG. 2 modifier keys such as Shift, Ctrl, and Alt are often allocated to the thumbs (e.g. U.S. Pat. No. 5,642,108 to Gopher et al. and U.S. Pat. No. 5,689,253 to Hargreaves et al.) or to palm presses, as in U.S. Pat. No. 5,017,030 to Crews. However, for a multi-touch surface, reaching the thumb for modifier keys poses the same drift exacerbation problems as reaching by the pinky, and palm touches should be ignored to encourage hand resting. Thus there exists a need in the multi-touch and chord keying art for alternative methods to activate modifier keys without drawing any fingers away from home row.
In its primary aspect, this invention introduces four-fingertip modifier chords to eliminate the hand twist and reach traditionally required to activate modifier keys. Simultaneously dropping the four long fingertips of a hand into a modifier zone on or near the home row keys applies the Shift modifier to subsequent typing or pointing input so long as any finger from the modifier chord remains touching the surface. Typically, then, the modifier will apply to activity by the opposite hand, but the present invention also lets a hand modify its own typing, thereby allowing capitalization of whole words, if at least one of its modifier chord fingertips remains touching as others lift to strike nearby keys. The four-fingertip (excluding the thumb) chord is preferred for this role because it is the easiest to drop and hold on the surface besides the five-finger chord, which must be reserved for hand resting.
Since the four-fingertip chord is also preferred for window scrolling, and since it is often a prelude to dropping the thumb into the full five-finger hand resting chord, the present invention takes special precautions to prevent accidental modifier activation. The modifier press signal is not sent to the host computer immediately upon detection of the modifier chord touchdown. The modifier press will only be sent, commiting the modifier, upon detection of modifiable input activity by other than the thumb of the modifying hand. Modifiable input activity can include any user action that produces a keypress, pointing, dragging, clicking or other command for the host computer, but does not typically include resting touches that cause no signals to be output. Any touch by the modifying hand""s thumb detected before commit will immediately cancel the modifier chord, effectively turning it into a hand resting chord. Such thumb touches after the modifier press or commit need not permanently cancel the modifier. However, if these thumb touches represent editing keys such as Space or BackSpace keypresses, the Shift modifier signal may release temporarily while the thumb key is transmitted since the typist is most likely just erasing or putting a normal space between two capitalized words.
Restricting the Shift modifier chord to a zone along home row encourages typists to return their hands to the home typing position. Furthermore, this allows a Ctrl modifier zone to be established along the row of keys above home row, an easy stretch from home row. A third modifier zone can be established along the row of keys below home row for rarer modifiers such as Alt, Windows, Open Apple, or Meta. Even a fourth modifier zone is possible approximately two key rows below home row. Note that all of these modifier zones can be reached through straight flexion or extension of the fingers from their home row position-absolutely no twisting or rotation of the wrist or fingers is necessary.
According to the present invention, multiple modifiers are activated by the same hand simultaneously when the fingertips of the modifier chord are clearly distributed into different modifier zones. To compensate for the natural arch in a row of fingertips, the vertical offset of each finger is measured relative to the home row key the finger normally rests upon. Accidental activation of a multiple zones is prevented by checking for a minimum interval between the vertical offsets of fingertips in different zones. If this condition is not met, the average of the vertical fingertip offsets is used to choose a single modifier zone. Distributing the fingertips into different zones does imply some finger twisting, but does not cause as much hand drift as reaching for multiple modifier keys on the periphery of the key layout.
In an alternative embodiment of this invention, different modifiers can be activated in a manner independent of any zones or the overall hand position on the surface. Rather, they are distinguished by different horizontal and vertical separations between the four fingertips performing the chord. Shift, for example, might be activated by the normal relaxed placement of four fingertips in a row with about 2 cm (xc2xexe2x80x3) separating the fingertip centers. Ctrl would then be activated by placing the fingertips stretched along the row with an average 3 cm (1xe2x85x9xe2x80x3) separation between them. A third modifier could be activated by splitting the fingertips vertically into two rows a couple cm apart. This aspect of the invention is most useful for non-typing situations where hand motions are not focused around a default position along home row. With this aspect, a hand can, for instance, apply different modifiers to mouse clicking activity on the opposite hand without having to reposition itself within certain modifier zones.
A primary objective of the present invention is to provide an apparatus capable of detecting four-fingertip modifier chords that obviate the awkward pinky or thumb reaches previously needed to strike and hold modifier keys.
Another objective of this invention is to prevent spurious modifier chord activation when the user is slowly relaxing into a hand resting chord, but does not initially have the thumb on the surface.
A further objective of this invention is to allow use of the Shift modifier chord for capitalization across words without applying the Shift modifier to intervening Space or BackSpace key activations by thumbs.
Yet another objective of this invention is to establish different modifier zones across, above, and below the home row of keys that can be utilized to apply different modifiers.
A further objective of this invention is to support simultaneous activation of multiple modifiers with the same hand when the fingertips of the modifier chord are clearly distributed among different modifier zones.
Another objective of this invention is to support selection of different modifiers from the relative arrangement of fingertips within a modifier chord rather than their placement within any particular zone on the surface.